CN1211955C - Optical signal transmission system and wide-range magneto-optical modulator in the said system - Google Patents

Optical signal transmission system and wide-range magneto-optical modulator in the said system Download PDF

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Publication number
CN1211955C
CN1211955C CNB011393076A CN01139307A CN1211955C CN 1211955 C CN1211955 C CN 1211955C CN B011393076 A CNB011393076 A CN B011393076A CN 01139307 A CN01139307 A CN 01139307A CN 1211955 C CN1211955 C CN 1211955C
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magneto
optic
unit
frequency
optical modulator
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CN1357978A (en
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峯本尚
伊藤伸器
石河大典
石塚訓
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/09—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on magneto-optical elements, e.g. exhibiting Faraday effect
    • G02F1/095—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on magneto-optical elements, e.g. exhibiting Faraday effect in an optical waveguide structure
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/09—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on magneto-optical elements, e.g. exhibiting Faraday effect
    • G02F1/092—Operation of the cell; Circuit arrangements

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Optical Communication System (AREA)
  • Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Abstract

An optical signal transmission system equipped with a magneto-optical modulator is provided. The magneto-optical modulator works to modulate an optical beam emitted from a light source and consists of a polarizer, a magneto-optical element, an analyzer, a dc field generator, a high-frequency field generator, and an impedance adjuster. The dc field generator works to apply a dc bias field to the magneto-optical element. The high-frequency generator is responsive to the high-frequency signal from said high-frequency signal generator to apply a high-frequency field to the magneto-optical element. The impedance adjuster works to adjust impedance of the high-frequency field generator for establishing effective transmission of the high-frequency signal to the high-frequency field generator, thereby increasing a modulation range up to frequencies higher than an upper limit of typical magneto-optical modulators. The application of the dc bias field and use of the impedance adjuster realizes the magneto-optical modulator which is useful up to a ferromagnetic resonance frequency.

Description

The magneto optical modulator of light signal transmission system and wide region modulation in this system
Technical field
The present invention relates generally to a kind of light signal transmission system, with a kind of improvement structure that is used for the magneto optical modulator that uses in identical transmission system, it is used for utilizing Faraday effect (Faraday effect) to go modulated beam of light to reach higher frequency.
Background technology
The most of external optical modulator that adopts in typical light signal transmission system utilizes electro optic effect (that is PockeFs effect).Especially, the most of light signal transmission systems that use in optical communication adopt the optical waveguide modulator that utilizes LiNbO3 crystal (for example, by " optic integrated circuit " that ohm company publishes, Nishihara and other, pp.298-304 (1985)) electro optic effect.Yet, use the optical modulator of this electrooptic crystal to be subjected to direct current (dc) drift (for example, J.Appl.Phys. volume 76, No.3.pp.1405-1408 (19941)) or optical damage, and keeping having certain difficulty aspect the permanent reliability of using.Alleviate above-mentioned characteristic degradation and relate to the increase of manufacturing cost.
In recent years, proposed light signal transmission system, it receives electric wave through an antenna, and applies it to an electrooptics modulator with the form of high-frequency signal (for example, Japan Patent is at first announced No.4-172261 and 10-186189).
The magneto optical modulator that utilizes magneto optical effect after deliberation a lot of years (for example, Appl.Phys.Lett. rolls up 21 No.8, pp.394-396 (1972)).But, because their response frequency is lower than the frequency of electrooptics modulator, they are not still in the application of reality, thereby be used as the usefulness of research optical magnetic field probe or current sensor (for example J.Appl.Phys. rolls up 53 No.11.pp.8263-8265 (1982) and national technical report, rolls up 38 No.2.pp.127-133 (1992)).
Japan Patent announces that first No.7-199137 has instructed the magneto optical modulator that uses as light polarization modulator in light signal transmission system.Yet the reactivity of this magneto optical modulator is low to tens kHz.U.S. Patent No. 6.141.140 has instructed the optical isolator that uses as magneto optical modulator, but its reactivity also is very low.This is because general optical isolator is coated with metal parts usually or utilizes metamagnet to be used to apply D.C. magnetic field in this, make the application of radio-frequency field will cause the generation of eddy current, this makes and is difficult to apply from the outside of optical isolator radio-frequency field more than tens kHz.In fact, optical isolator uses as an optical modulator, uses the external magnetic field to cause light to be returned to the unwanted direction direction of light source (promptly towards), and has the shortcoming of change magneto optical effect (being Faraday effect) validity.
In recent years, also research (for example Appl.Phys Lett. rolls up 68 No.25.pp.3546-3548 1996 and extended abstract 61th meeting 2000) magneto optical modulator is used for measuring the electric current in the substrate of semiconductor conduction, and wherein the Dc bias field is applied in the crystal film of magneto-optic.Japan applied physics association, the 2000.4P-0-4 of Tokyo University).
Most of general light signal transmission systems are used to modulate the exciting current that is applied in semiconductor laser on higher frequency, perhaps utilize an optical waveguide modulator to represent electro optic effect (that is, ripple gram effect, Pockel ' s effect).Directly modulate the modulator that the exciting current that puts on semiconductor laser does not need a special use, therefore provide advantage to be, this light signal transmission system will be structurally simple.Yet, be difficult to modulate the light that is higher than several GHz from the frequency of semiconductor laser emission.In addition, in wanting modulation operations, the exciter of activating semiconductor laser may cause fault on upper frequency, perhaps because High Speed Modulation is difficult to send a far output based on laser linear frequency modulation.
In addition, in an optical signal transmission network that is made of many optical fiber, a light signal comprises the noise that occurs from a plurality of reflected waves that are installed in the opticator in each transmission line usually.For fear of this problem, adopt occasionally such as led light source with wide emission spectrum.But, wherein the LED frequency band that can be energized is approximately 100MHz and (sees Hiroo Yonetsu, " optic communication device engineering " by Kogaku Shpin publication, therefore pp.135-141 (1991)), need a special optical modulator to be used to modulate the output of LED on the frequency of 100MHz being higher than.
The optical waveguide modulator utilizes electro optic effect.In this case, laser beam or light that ripple gram effect (Pockel ' s effect) can High Speed Modulation be produced by LED, and can not run into the problem of chirp, but face the problem of dc shift and optical destructive as mentioned above.Alleviate these and relate to the manufacturing cost increase.In light signal transmission system, wherein the signal of telecommunication that is received by antenna is used for modulating a light beam (being optical carrier), and modulator is installed in open-air place usually, therefore will have the problem of dc shift and optical damage.In addition, great majority use the optical waveguide modulator of ripple gram effect to be designed to single pattern.Usually be difficult to produce and have the waveguide of tens μ m to the bigger core-diameter of hundreds of μ m.Therefore, the problem that the optical waveguide modulator runs into is, it is difficult to the output with the output of the output of High Speed Modulation LED, image intensifer or fiber laser (bigger than tens μ m core-diameters), LED needs optical fiber to have big core-diameter and is used to send enough light quantities, and the power supply of image intensifer is increased greatly.
Utilize the magneto optical modulator of Faraday effect also to be studied, it applies the crystal film that a Dc bias field is parallel to magneto-optic, and the crystal film of magneto-optic is installed in the transmission line place that makes on semiconductor or the microstrip line, and monitoring flow is crossed the current waveform of this lead.This structure monitoring flow is crossed the waveform of the electric current of the lead on Semiconductor substrate (for example Appl. physics Lett. rolls up 68 No.25, page or leaf 3546-3548 (1996)), the problem that faces be not adjusted on the substrate impedance of transmission line cause this corrugated gasket around.This structure can not use optical fiber as optical transmission line, and is not suitable for light signal transmission system.Another structure of the waveform of this microstrip line (for example, the 61st annual meeting of extended abstract 2000) electric current is flow through in measurement.Japan Applied Physics association, Tokyo University 2000,4p-Q-4, have an analyzer and be configured in the optical fiber back of the output of the unit that is connected to magneto-optic, the problem that causes is to increase fiber lengths will cause the light of linear polarization to be subjected to random polarization in optical fiber, therefore causes the output intensity of Modulation analysis device very difficult.In addition, above-mentioned magneto optical modulator is used to apply the crystal film that magneto-optic is given in the Dc bias field with the identical direction of direction that applies of radio-frequency field.The crystal film that the applying of the Dc bias field that the enough big crystal film that changes magneto-optic is a single-domain structure will cause magneto-optic is by magnetically saturated, therefore causes the numerical value of modulated output signal to reduce or the fault of output modulation signal.
Summary of the invention
Therefore a main purpose of the present invention is to avoid the shortcoming of prior art.
Another object of the present invention provide a kind of can be on wide region the improved structure of magneto optical modulator of modulated beam of light or carrier wave.
A further object of the present invention provides a kind of light signal transmission system that is equipped with magneto optical modulator, and it is higher for the reliability aspect that increases a period of time, and can transmit the light signal that does not have dc shift and optical damage.
According to one aspect of the present invention, provide a kind of light signal transmission system.This light signal transmission system comprises: (a) light source of an emission light beam; (b) high frequency signal generator that produces high-frequency signal; (c) modulation is from the magneto optical modulator of the light beam of light emitted; (d) transmission is by the optical fiber of the light beam of magneto optical modulator modulation; And (e) optical receiver of the modulated beam of light that sends via optical fiber of reception.This magneto optical modulator comprises the unit of a polarizer, a magneto-optic, an analyzer, a dc magnetic field generator, a radio-frequency field generator and an impedance regulator.The light beam of light emitted enters the unit and the analyzer of polarizer, magneto-optic in proper order.This dc magnetic field generator work is given the unit of magneto-optic to apply the Dc bias field.This radio-frequency field generator response applies the unit that a radio-frequency field is given magneto-optic from the high-frequency signal of described high frequency signal generator.The impedance regulator operation goes to adjust the impedance of radio-frequency field generator, is used to set up the effective transmission of high-frequency signal to the radio-frequency field generator.
The Dc bias field imposes on the unit of magneto-optic, and the use of the impedance regulator between high frequency signal generator and radio-frequency field generator can make magneto optical modulator go to produce at a high speed modulation, and this can not be realized by traditional magneto optical modulator.The realization of such High Speed Modulation belongs to the fact, through impedance regulator, the impedance adjustment of radio-frequency field generator is used for realizing the effective transmission of high-frequency signal to the radio-frequency field generator, and applying of radio-frequency field led 0 multidomain structure that causes magneto optical modulator and be converted into single-domain structure.Usually, the frequency response of moving of the domain wall between the magnetic domain of the unit of magneto-optic is limited to tens to hundreds of MHz, makes domain wall be higher than those scopes in frequency and can not respond.Therefore, can not use the unit of such magneto-optic with the optical modulator that is used for light signal transmission system of high-speed response a requirement.This problem can utilize structure of the present invention as mentioned above to solve.Particularly, the unit that the Dc bias field imposes on magneto-optic causes multidomain structure to be converted to one-domain structure, makes domain wall disappear, and therefore causes the mobile disappearance of domain wall, and domain wall is the decisive factor of modulation upper limiting frequency, therefore allows to increase modulating speed.
In the pattern that the present invention recommends, the unit of magneto-optic is made with the multidomain magneto-optic memory technique.Dc magnetic field generator produces the Dc bias field greater than the saturation field of the unit of magneto-optic.
The direction that the Dc bias field is applied to the direction of unit of magneto-optic and the unit that radio-frequency field is applied to magneto-optic is positioned in 90 ° ± 30 ° the scope.
Radio-frequency field is to the direction of easy magnetizing axis that direction can be positioned at the unit of magneto-optic that applies of the unit of magneto-optic.Have in the unit of magneto-optic under the situation of length, radio-frequency field is to the length direction that direction can be positioned to be parallel to substantially the unit of magneto-optic that applies of the unit of magneto-optic, and therefore the demagnetizing factor with the unit of magneto-optic minimizes.
This optical fiber keeps optical fiber to realize by gradient index fiber or polarisation.
Wherein this light beam is the input face of unit that inputs to the magneto-optic of this magneto optical modulator in 90 ° ± 15 ° scope.
This light source is by a realization of LED and fiber laser.
An image intensifer can be configured between light source and the magneto optical modulator.
Lens can be configured between light source and the magneto optical modulator.
A coupler can be provided, and it is connected to magneto optical modulator through optical fiber.Reflector can be configured on the end face of unit of the magneto-optic relative with input face, goes to produce the reflection by the light beam of the cells modulate of magneto-optic.This coupler also is connected to optical receiver and goes to guide the reflection of modulated beam of light to give optical receiver.
High frequency signal generator can be realized by an antenna that is used for receiving with the form of electric wave high-frequency signal, and launch this high-frequency signal and give the radio-frequency field generator.This antenna can be a kind of of Yagi aerial (Yagi antenna), loop aerial and parabolic antenna.
Send to described magneto optical modulator by a light beam in optical fiber and the lens with described light emitted.
According to another aspect of the present invention, provide a kind of magneto optical modulator.This magneto optical modulator comprises: (a) light beam inputs to its polarizer; (b) reception is from the magneto-optic unit of the light beam of described polarizer; (c) output is from the analyzer of the light beam of the unit of described magneto-optic; (d) one is carried out work so that apply the dc magnetic field generator that the unit of magneto-optic is given in the Dc bias field; (e) one is carried out work so that apply the radio-frequency field generator that radio-frequency field is given the unit of magneto-optic; (f) one is carried out work so that adjust the impedance regulator of the impedance of radio-frequency field generator.
In the pattern that the present invention recommends, the unit of magneto-optic is to be used in the magneto-optic memory technique that has multidomain structure under the situation that does not apply the Dc bias field to make.Dc magnetic field generator produces the Dc bias field greater than the saturation field of the unit of magneto-optic.
The direction that the Dc bias field imposes on the direction of unit of magneto-optic and the unit that radio-frequency field imposes on magneto-optic is positioned in 90 ° ± 30 ° the scope.
Radio-frequency field is to the direction of easy magnetizing axis that direction can be positioned at the unit of magneto-optic that applies of the unit of magneto-optic.Have in the unit of magneto-optic under the situation of length, radio-frequency field is to the length direction that direction can be positioned to be parallel to substantially the unit of magneto-optic that applies of the unit of magneto-optic, and therefore the demagnetizing factor with the unit of magneto-optic minimizes.
The unit of magneto-optic can be made up of a bulk of crystal, polycrystal sintered body, a crystal film or the synthetic that comprises resin and be dispersed in the magneto-optic memory technique in the resin.
The unit of this magneto-optic can be made by bilateral garnet crystal film.
The frequency of radio-frequency field is 200MHz or higher.This impedance regulator can be realized by the filter that a high-frequency signal that is designed to allow pre-selected frequency therefrom passes through, and is used to described radio-frequency field generator or is designed to have the resonator of the high-frequency signal of pre-selected frequency resonance.
Interchangeable, this impedance regulator can be realized by the filter that a high-frequency signal that is designed to allow two different frequencies therefrom passes through at least, and is used to described radio-frequency field generator or is designed to have the resonator of the high-frequency signal of different frequency resonance.
This dc magnetic field generator can be realized by permanent magnet.Each of this permanent magnet is by Ferrite Material, based on SmCo (Sm-Co) material with based on a kind of the making of neodymium iron boron (Nd-Fe-B) material.
Alternatively, this dc magnetic field generator can provide electric current to constitute to the dc generator of this electromagnet by an electromagnet and one.
This dc magnetic field generator can design with geometry, makes to form a closed substantially magnetic circuit.
The unit of polarizer, magneto-optic and analyzer can be produced on the single substrate.
The unit of polarizer, magneto-optic and analyzer can be inserted between the setting ruler in line.
This radio-frequency field generator can be placed on the end face of unit of this magneto-optic.
The unit of this magneto-optic is to locate like this, makes light beam input to an input face of the unit of this magneto-optic in 90 ° ± 15 ° scope.
This radio-frequency field generator can be realized to the coil within 1000 mu m ranges at 10 μ m by its minimum diameter.
Alternatively, the unit of this magneto-optic can be made by a light wave guider of being made by the garnet crystal film.
This impedance regulator can be made up of a transverse electro-magnetic wave unit and a non-reflexive terminate load.
This impedance regulator can be designed to can be in given frequency resonance.
An electromagnetic wave shielding shell further can be provided, comprise unit, analyzer and the radio-frequency field generator of polarizer, magneto-optic therein.
Description of drawings
From given hereinafter detailed description and the accompanying drawing followed from the preferred embodiments of the present invention, invention will be more fully understood, but can not limit the present invention for specific embodiment, but the purpose in order to explain and to understand only.
In the accompanying drawings:
Fig. 1 is a block diagram, and the light signal transmission system that is equipped with magneto optical modulator according to a first embodiment of the invention is shown;
Fig. 2 is a block diagram, and the light signal transmission system that is equipped with according to the magneto optical modulator of second embodiment of the present invention is shown;
Fig. 3 is a block diagram, and the light signal transmission system that is equipped with according to the magneto optical modulator of the 3rd embodiment of the present invention is shown;
Fig. 4 is a block diagram, and the light signal transmission system that is equipped with according to the magneto optical modulator of the 4th embodiment of the present invention is shown;
Fig. 5 is a block diagram, and the light signal transmission system that is equipped with according to the magneto optical modulator of the 5th embodiment of the present invention is shown;
Fig. 6 is a block diagram, and the light signal transmission system that is equipped with according to the magneto optical modulator of the 6th embodiment of the present invention is shown;
Fig. 7 is a block diagram, and the light signal transmission system that is equipped with according to the magneto optical modulator of the 7th embodiment of the present invention is shown;
Fig. 8 is a perspective view, and the direction that applies of the Dc bias field of unit of magneto-optic of first embodiment that is used for Fig. 1 and radio-frequency field is shown;
Fig. 9 is a curve chart, illustrates and do not have the frequency response characteristic of the Dc bias field of the magneto-optic unit that puts on first embodiment that is used for Fig. 1;
Figure 10 is a curve chart, the frequency response characteristic of the unit of the magneto-optic of first embodiment when being illustrated in the no resistance adjuster;
Figure 11 is a block diagram, and the light signal transmission system according to the magneto optical modulator of the 8th embodiment of the present invention is shown;
Figure 12 is a curve chart, and the example according to the frequency characteristic of the magneto optical modulator of the 9th embodiment of the present invention is shown;
Figure 13 is a curve chart, and another example according to the frequency characteristic of the magneto optical modulator of the 9th embodiment of the present invention is shown;
Figure 14 is a block diagram, and the magneto optical modulator according to the of the present invention ten embodiment is shown;
Figure 15 (a) is a perspective view, and the magneto optical modulator according to the 11 embodiment of the present invention is shown, and has therefrom removed dc magnetic field generator;
Figure 15 (b) is a perspective view, and the magneto optical modulator of the 11 embodiment is shown;
Figure 16 is a block diagram, and the magneto optical modulator according to the 12 embodiment of the present invention is shown;
Figure 17 (a) is a front view, and the structure that is installed in according to the radio-frequency field generator in the magneto optical modulator of the 13 embodiment of the present invention is shown;
Figure 17 (b) is a perspective view, and the magneto optical modulator according to thirteenth embodiment of the invention is shown;
Figure 18 is a block diagram, and the magneto optical modulator according to the 14 embodiment of the present invention is shown;
Figure 19 (a) is a plane graph, and the optical modulation equipment according to the 15 embodiment of the present invention is shown; With
Figure 19 (b) is a perspective view, and the magneto optical modulator of the 15 embodiment is shown.
Embodiment
With reference to the accompanying drawings, wherein in several figure unless otherwise mentioned, have similar structure by the part of same term appointment, especially Fig. 1 shows a light signal transmission system that is equipped with magneto optical modulator 150 according to a first embodiment of the invention.
Pass optical fiber 8 from the optical carrier or the light of light source 101 emissions, and enter magneto optical modulator 150, magneto optical modulator 150 utilizes the Faraday effect (Faraday effect) of the unit 1 of magneto-optic.Magneto optical modulator 150 is made of the unit 1 of a polarizer 2, magneto-optic, analyzer 3, radio-frequency field generator 5, an impedance regulator 6 and a dc magnetic field generator 4.Crystal film that the unit 1 of magneto-optic is for example formed by vapor phase epitaxy by a bulk of crystal for example, polycrystal sintered body, one or the synthetic that comprises resin and be dispersed in the ferromagnet optical material in the resin are formed.Radio-frequency field generator 5 works to apply the unit 1 that radio-frequency field is given magneto-optic.Impedance regulator 6 works to adjust the electrical impedance of radio-frequency field generator 5.Magneto optical modulator 150 responses are from the signal of telecommunication (being high-frequency modulation signal) of high frequency signal generator 7 inputs, the light relevant with this high-frequency modulation signal that modulation sends through optical fiber 8.The light of modulation is exported through optical fiber 9, and is converted to the signal of telecommunication in optical receiver 102, through amplifier and the demodulation successively of signal processing circuit (not shown).
The impedance of radio-frequency field generator 5 is adjusted in impedance regulator 6 operations, so that set up effective transmission of the signal from high frequency signal generator 7 to radio-frequency field generator 5.Figure 10 be illustrated in and no resistance adjuster 6 between contrast.Under illustrational situation, radio-frequency field generator 5 is made up of around the wiring of the unit 1 of magneto-optic 16 to tens corrals.Under the situation that does not have impedance regulator 6, magneto optical modulator 150 carries out work and only modulates the low-frequency input signal that is lower than about 1MHz, and is therefore inoperative when frequency is higher than a few MHz as optical modulator.This is because radio-frequency field generator 5 has big induction reactance usually and goes to stop high-frequency current to flow through.Such as will be discussed below, even the Dc bias field is applied in the unit 1 of magneto-optic, under the situation that does not have impedance regulator 6, this frequency characteristic is not improved.
Applying the Dc bias field will discuss with reference to figure 8 and 9 to the effect of the unit 1 of magneto-optic.Usually, under the situation that does not have the Dc bias field, ferrimagnetic material and ferromagnet such as ferrite, garnet or transition metal keep multidomain structure.Especially, magneto-optic memory technique such as ferrite and garnet tens and hundreds of MHz between frequency with the mobile resonance that presents of domain wall, approach to be used for the modulating frequency of general light signal transmission system.Believing in this field to use such magneto-optic memory technique to be used for the magneto optical modulator that adopts at light signal transmission system.Yet, we have found that the Dc bias field is applied to the magnetic domain decreased number that magneto-optic memory technique will cause this material, the saturation field that the application of Dc bias field reaches this material will cause the formation of single-domain structure, therefore reduce or eliminate in modulation harmful effect with the resonance that moves of domain wall.
As shown in Figure 8, the Dc bias field will be discussed below put on the unit 81 of magneto-optic in given angle (for example right angle), radio-frequency field is to the direction that applies of the unit 81 of magneto-optic.Notice that as shown in the figure the Dc bias field can be positioned at D.C. magnetic field and apply direction A, D.C. magnetic field applies direction B or any in the plane direction comprises that D.C. magnetic field applies direction A and B.
When the Dc bias field is positioned perpendicular to radio-frequency field, will obtain a bigger modulation degree, but when the direction of Dc bias field during to the applying direction and be positioned in 90 ° ± 30 ° of radio-frequency field, modulation degree can not reduce widely.Particularly, in the time of in its direction is positioned at those scopes, the Expected Results of Dc bias field will be obtained.
The unit 81 that causes magneto-optic that applies of Dc bias field has single-domain structure.Therefore, when radio-frequency field is applied in the unit 81 of magneto-optic, can not produce resonance with moving of domain wall, the resonance frequency of domain wall is to arrive within hundreds of MHz scopes tens.Further, can suitably keep magneto optical effect (that is), the ferro resonance frequency of (intensity that depends on bias field is that several GHz are to 100GHz) up to the unit 81 that reaches magneto-optic by the optical modulation of Faraday effect.Particularly, this magneto optical modulator 150 is being lower than running normally under the ferro resonance frequency.In addition, when the direction of propagation of light when being parallel with the direction of the radio-frequency field of the unit 81 that puts on magneto-optic, will cause Dc bias field and radio-frequency field vector and component and parallel light extend and go to provide magneto optical effect or modulation.
Therefore, light signal transmission system can be set up the high frequency modulated of light beam, can use to apply the Dc bias field and realize for radio-frequency field generator 5 for the magneto optical modulator 150 and the input high-frequency signal of the unit 1 of magneto-optic.
The direction of propagation of light need not always be in that to put on the direction of unit 81 of magneto-optic parallel with radio-frequency field.From the catoptrical influence of the end of end face of the unit 81 of magneto-optic or optical fiber 8 and 9 by changing light the direction of propagation and the direction that applies of radio-frequency field in ± 15 ° of scopes, eliminate to each other.
Fig. 9 illustrates the frequency characteristic of light signal transmission system as shown in Figure 1.The bilateral garnet crystal film of unit 1 usefulness of magneto-optic is made.Under the situation of the Dc bias field that does not produce by dc magnetic field generator 4, with the mobile modulated light signal of domain wall at about 200MHz resonance.Particularly, be higher than on the 200MHz modulating frequency, magneto optical modulator 150 can not normally turn round.In other words, when being applied the Dc bias field by dc magnetic field generator 4 and give the unit 1 of magneto-optic, frequency characteristic is enhanced.Especially, even when Dc bias field more than or equal to the saturation field of the unit 1 that is applied in magneto-optic the time, magneto optical modulator 150 runnings go to set up the modulation that reaches about 3GHz.Notice Hdc represent to run through accompanying drawing the Dc bias field apply direction.
Radio-frequency field applies direction and can locate direction along its easy magnetizing axis to the unit 81 of magneto-optic.In addition, have under the situation of length in the unit 81 of magneto-optic, the length direction that radio-frequency field is parallel to the unit 81 of magneto-optic substantially applies and will cause its demagnetization factor to be reduced to minimum.Applying under the radio-frequency field of low degree, this can easily produce the lofty tone system of light signal.
Light source 101 can be made of a semiconductor laser, a LED (light-emitting diode) or a fiber laser.Optical fiber 8 and 9 can keep optical fiber, gradient index fiber or large diameter optical fiber to make by single pattern optical fiber, polarisation.When optical fiber 8 keeps optical fiber to realize by polarisation, light source 101 is realized by the light source such as the semiconductor laser of launching linearly polarized photon, be held constant from the polarised direction of the light of light source 101 emission, reach the unit 1 of magneto-optic, therefore allow to omit this polarizer 2 up to light.
Below with reference to Fig. 2 second embodiment will be described.
Directly enter lens 28 from the light of light source 201 emissions, and reach polarizer 22.When lens 28 were used to produce the parallel rays of light, it was convenient on optical fiber 9 easily that light compiles, but need not be parallel all the time from the light of the light of lens 28 outputs.
The light that inputs to polarizer 22 enters the unit 21 of magneto-optic then through linear polarization, and wherein its plane of polarization is rotated by the radio-frequency field that radio-frequency field generator 25 applies.Light enters analyzer 23 then, and is changed on intensity or modulates, and is defined as the plane of polarization that rotates.The light of modulation enters optical fiber 9 through lens 29, and is sent to optical receiver 202, is converted into the signal of telecommunication therein, through amplifier and the demodulation successively of signal processing circuit (not shown).Dc magnetic field generator 24, radio-frequency field generator 25, impedance regulator 26 and high frequency signal generator 27 are equal to dc magnetic field generator 4, radio-frequency field generator 5, impedance regulator 6 and the high frequency signal generator 7 in Fig. 1, will omit their detailed explanation here.
Usually, the light that is produced by the LED exciting current that is used for LED by direct modulation can be modulated and only reach 100MHz.Yet the use of the magneto optical modulator 250 of this embodiment can make the light that is produced by LED be modulated onto several GHz or higher.Therefore, magneto optical modulator 250 can be used for light signal transmission system, and wherein a plurality of optical fiber are tangled, and this causes that on optical signal transmission line the optical noise from a plurality of reflection of lights of optical fiber connector takes place.
Light source 201 can be realized by the light beam that semiconductor laser produces linear polarization.In this case, the direction of the direction of the polarization surface that produced by light source 201 of coupling and polarizer 22 has been eliminated the needs to polarizer 22.
Below with reference to Fig. 3 the 3rd embodiment will be described.
Pass optical fiber 320 from the light of light source 301 emissions, in image intensifer 380, be exaggerated.The light that amplifies passes optical fiber 321, and enters magneto optical modulator 350.Image intensifer 380 can be realized by a fiber amplifier or semiconductor laser amplifier.In this embodiment, fiber amplifier is used to produce an intensity output.Provide a modulation signal to remove to modulate the light of input to the unit 31 of magneto-optic by high frequency signal generator 37 and impedance regulator 36.The light of modulation is sent to optical receiver 302 through optical fiber 322 in magneto optical modulator 350, and is converted into the signal of telecommunication, through amplifier and the demodulation successively of signal processing circuit (not shown).Other layout is the same with in Fig. 1 those, will omit their detailed explanation here.
In this embodiment, light source 301 can be made of a LED or a fiber laser, and its output light is difficult to High Speed Modulation usually by the exciting current that is modulated in LED or the optical pump source in fiber laser.The magneto optical modulator 350 of this embodiment can be to be higher than the velocity modulation input light of several GHz.The use of image intensifer 380 can transmit the light modulated of Large-power High-Speed, therefore allows to distribute to a plurality of optical receivers with the power of expectation through branch optical fiber from the light signal of optical fiber 9 outputs.When the rational number of branch optical fiber depends on the modulating frequency of light signal and the fiber distance that is sent out the time, the light signal transmission system that uses in Fig. 3 allows light signal to be assigned to 100 to be positioned at the optical receiver that leaves magneto optical modulator 350 about 1km.
In Fig. 3, magneto optical modulator 350 is positioned at the back of image intensifer 380, but according to S/N than the back that can be set to be right after at light source 310.
Below with reference to Fig. 4 to 7 the 4th to the 7th embodiment will be discussed.
Fig. 4 illustrates a light signal transmission system according to the 4th embodiment, and the place that it is different from first embodiment of Fig. 1 only is that antenna 430 is as high frequency signal generator.Other layout is identical, will omit their detailed explanation here.
Antenna 430 receives the signal of for example exporting from the radio base station or the portable remote-terminal of mobile phone, and it gives radio-frequency field generator 45 through impedance regulator 46 outputs.Radio-frequency field generator 45 produces 200MHz or higher radio-frequency field.This can make the signal that is received by antenna 430 carry to optical receiver 402 on the light signal that inputs to magneto optical modulator 450.When civilian power supply came into force, high-frequency amplifier can be arranged on the back of antenna 430 and impedance regulator 46.
Fig. 5 illustrates a light signal transmission system according to the 5th embodiment, and wherein reflexive magneto optical modulator 550 is used to replace such as the transmission magneto optical modulator that adopts in each of first to fourth embodiment.The signal that the high frequency signal generator 57 that the use permission of reflexive magneto optical modulator 550 is made of antenna receives carries to optical receiver 502 through single optical fiber 58.This causes system's manufacturing cost to reduce.
Magneto optical modulator 550 has a reflector 508 that is arranged on 51 back, unit of magneto-optic.Optical signals reflector 508 reflections that manifest from the unit 51 of magneto-optic, and enter polarizer 52 once more, make that its intensity is modulated, and output to optical receiver 502 through coupler 505.Particularly, polarizer 52 also plays analyzer, and it allows the light signal of modulation to be sent out hundreds of rice to tens kilometers through optical fiber 58.Coupler 505 can be a known type, and its detailed explanation will here be omitted.
Fig. 6 illustrates a light signal transmission system according to six embodiment different with the 5th embodiment of Fig. 5, be that Yagi aerial (Yagi antenna) 630 is used as high frequency signal generator work, so that the unit of high-frequency modulation signal to magneto-optic to be provided.Other layout is the same with in Fig. 5 those, will omit their detailed explanation here.
Fig. 7 illustrates the light signal transmission system of a use loop aerial 730 as high frequency signal generator.Other layout is the same with in Fig. 6 those, will omit their detailed explanation here.The use of loop aerial 730 causes the reduction of antenna impedance, and this is convenient to easily and impedance matching when the magneto-optic modulating unit of front wheel driving.Alternatively, parabolic antenna or box horn can be used.
Figure 11 illustrates a light signal transmission system that is equipped with according to the magneto optical modulator of the 8th embodiment of the present invention.
Pass optical fiber 1108 from the light of light emitted, and in lens 1120, be converted into collimated light beam.The light that comes out from lens 1120 passes through polarizer 1102, and by linear polarization.The light of linear polarization enters the unit 1101 of magneto-optic, makes to utilize the radio-frequency field that is produced by radio-frequency field generator 1105 that plane of polarization is rotated, and after this it passes through analyzer 1103, and modulated in the intensity relevant with the rotation of plane of polarization.The light of intensity modulated by lens 1121 polymerizations, is used to send to the optical receiver (not shown) at the end of optical fiber 1109.
Lens 1120 play a part to guide effectively the light that sends through optical fiber 1108 to polarizer 1102.Lens 1121 play to guide effectively outputing on the optical fiber 1109 of analyzer 1103.Yet, very little if the thickness of the unit 1101 of polarizer 1102, magneto-optic and analyzer 1103 is done, cause optical loss to reduce, lens 1120 and 1121 can omit.Layering by metal and dielectric layer, anyly have high birefringence or a polarised light separative element crystal, the polarisation separator that constitutes such as the multilayer that is made of high refraction materials and low refraction materials can be realized the attenuation of polarizer 1102.Can realize the attenuation of the unit 1101 of magneto-optic by bilateral garnet crystal thin film fabrication.
Dc magnetic field generator 1104 is identical with in the above-described embodiments that in structure and operating aspect.Particularly, dc magnetic field generator 1104 works to apply the unit 1101 that magneto-optic is given in the Dc bias field, to alleviate or to eliminate the influence of the multidomain structure of the unit 1101 of magneto-optic in modulation.Put on that the direction of Dc bias field of the unit 1101 of magneto-optic usually is not limited to be represented by Hdc in the drawings, but when its with the radio-frequency field of the unit 1101 that puts on magneto-optic by radio-frequency field generator 1105 apply direction when consistent, it may not be modulated or lead to the failure in the modulation degree that produces expectation.Therefore, the Dc bias field for radio-frequency field to apply that direction is positioned within 90 ° ± 30 ° be rational.The numerical value of Dc bias field enough reduces the domain wall number of the unit 1101 of magneto-optic, yet still, dc magnetic field generator 1104 puts on the saturation field of the Dc bias field of the unit 1101 with single-domain structure magneto-optic less times greater than the unit 1101 of magneto-optic in this embodiment.
Be similar to the above embodiments, impedance regulator 1106 is used for changing the impedance of radio-frequency field generator 1105, so that improve the radio-frequency field that is converted to from the high-frequency signal of high frequency signal generator (not shown), is used for setting up modulation on desired frequency.
Preferably radio-frequency field is positioned in direction along easy magnetizing axis to the direction that applies of the unit 1101 of magneto-optic, that is to say, direction is substantially perpendicular to the bilateral garnet crystal film direction of the unit 1101 of magneto-optic.Therefore applying under the radio-frequency field of low degree, can set up the lofty tone system of light signal.
Be similar to the above embodiments, the use of Dc bias field and impedance regulator 1106 can make light signal modulated with the frequency that is higher than 200MHz.
Radio-frequency field generator 1105 is realized by a coil.For example, this coil have 50 the circle, 15 the circle, 5 the circle or still less and 1 the circle situation under, the magneto optical modulator of this embodiment plays modulated light signal respectively and reaches 200MHz, 1GHz, 3GHz and 10GHz.
Light signal transmission system according to the 9th embodiment will be discussed below, wherein only be the internal structure of impedance regulator 1106 with that the difference shown in Figure 11.Other layout is identical, will omit their detailed explanation here.
Impedance regulator 1106 is used to carry out resonance function or filter function, and it is used for setting up bigger modulation degree on concrete frequency.Impedance regulator 1106 can be realized that inductance and electric capacity are arranged so that like this circuit can allow the signal of given frequency by it in given frequency resonance or filter by the resonant circuit that comprises inductance and electric capacity.Figure 12 illustrates the situation that the frequency that is used for resonance is 0.8 GHz and 1.2GHz.Figure 13 illustrates the situation that the frequency that is used for resonance is 0.8GHz, 1.6GHz and 2.4GHz.The use of impedance regulator 1106 defines modulation band, but produces bigger modulation degree on the centre frequency of modulation band.The modulation degree of comparing when in this embodiment, being designed to hardly resonance with impedance regulator 1106 increases about 5 to 10dB or more.
Figure 14 illustrates a light signal transmission system according to the of the present invention ten embodiment, wherein only is the structure of dc magnetic field generator with the 9th the embodiment difference of Figure 11.Other layout is identical, will omit their detailed explanation here.
Dc magnetic field generator produces the soft magnetic core 1452 that coil 1451 and shape approach magnetic circuit by a dc generator 1450, D.C. magnetic field and constitutes.D.C. magnetic field produces coil 1451 and is made up of about 500 circle leads.Dc generator 1450 is used for changing and offers the current value that D.C. magnetic field produces coil 1451 when needing, and rise to adjust produce the Dc bias field that coil 1451 produces by D.C. magnetic field numerical value in 0 to 1 tesla (promptly, therefore 0 to 10000 Gauss) effect within the scope can make this material of the unit 1401 of the numerical value of Dc bias field and magneto-optic match.Particularly, only offer current value that D.C. magnetic field produces coil 1451 by dc generator 1450 to go to control the Dc bias field be possible, so compensating direct current bias voltage field changes institute by environment temperature and causes numerical value change by adjusting.
Figure 15 (a) and 15 (b) illustrate the magneto optical modulator according to the 11 embodiment of the present invention, and wherein two rulers 1570 and 1571 are configured in the unit 1501 of polarizer 1502, magneto-optic and the outside of analyzer 1503.Figure 15 (a) illustrates the magneto optical modulator of therefrom having removed dc magnetic field generator 1540.
The light that sends through optical fiber 1521 enters the magneto optical modulator that unit 1501 and analyzer 1503 by ruler 1570 and 1571, polarizer 1502, magneto-optic constitute.The unit 1501 of polarizer 1502, magneto-optic does not have lens with analyzer 1503 use adhesive with the form of chip and links to each other.This chip is inserted between the end face of ruler 1570 and 1571, connects or is glued therewith, is clamped the inside of the slot sleeve of being convenient to see 1580 as indicated by dashed line tightly by a slot sleeve 1580.
Ruler 1570 and 1571 and each mixture of slot sleeve 1580 by nonmagnetic and nonmetallic materials such as pottery, glass, resin or various filler and resin constitute, they can not produce eddy current for applying of radio-frequency field.Be similar to the above embodiments, radio-frequency field generator 1505 is coupled to the high frequency signal generator (not shown) through impedance regulator 1506, high frequency signal generator configuration aspects be with each of the above embodiments in that be identical.
As being made by the columniform permanent magnet of a sky at the dc magnetic field generator 1540 as shown in Figure 15 (b), it forms a slit therein and removes to limit magnetic pole strength, and the magneto optical modulator of combination is set between magnetic pole strength.Particularly, dc magnetic field generator 1540 is to design like this, makes to produce closed substantially magnetic loop except that slit.Compare with the dc magnetic field generator 1104 that is made of permanent magnet shown in Figure 11, the dc magnetic field generator 1540 of this embodiment can produce the unit 1501 that magneto-optic is removed to put in strong relatively Dc bias field.In the level of the dc magnetic field generator 1104 that the numerical value that keeps the Dc bias field is equaling Figure 11 substantially, the size that reduces dc magnetic field generator 1540 also is possible.In addition, the use of closed magnetic circuit causes the reduction of demagnetizing factor, guarantees the thermal stability of Dc bias field, and keeps a constant long-term time of numerical value of Dc bias field.This causes improving the reliability of magneto optical modulator.
The magneto optical modulator of present embodiment plays modulated light signal and reaches 5GHz.When needs reduce or eliminate from the end face of ruler 1570 and 1571 reflective, ruler 1570 and 1571 end face can be polishing to its longitudinal centre line and/or terminal about 15 or littler angle of the unit 1501 of polarizer 1502, magneto-optic, and the unit 1501 and the analyzer 1503 of analyzer 1503, magneto-optic can be coated with invalid coating jointly.Have the numerical value that the unit 1501 of ruler 1570 and 1571, polarizer 1502, magneto-optic of the end face of inclined-plane and polishing and use with analyzer 1503 of invalid coated end cause turning back to the light of light source and reduce 40db or littler.Semiconductor laser light source formation in cheapness is gone under the situation of outgoing laser beam, be difficult to by directly modulating with High Speed Modulation, we notice that the reflected wave of laser beam from the magneto optical modulator of combination does not have the optics fluctuation to take place, and this laser beam can be modulated and reaches 5GHz.
Other device is the same with in the above-described embodiments those.The magneto optical modulator of present embodiment can be used for aforesaid any one light signal transmission system.
Figure 16 illustrates a magneto optical modulator according to twelveth embodiment of the invention, and wherein the unit 1601 of polarizer 1602, magneto-optic, analyzer 1603 and dc magnetic field generator 1604 are to be assemblied in the single substrate 1690.
As seeing from figure, substrate 1690 is to be formed by the rectangular slab of making such as nonmagnetic substances such as resin, resin extender synthetic, ceramic material or glass.In this embodiment, substrate 1690 usefulness glass ring oxidation things are made, i.e. glass ring oxidation thing is a kind of easily by the mach resin extender synthetic of accurate diamond saw (being also referred to as scribing machine).Substrate 1690 has two recess or the chambeies that form at its surperficial central portion, is used for the installation and a horizontally extending groove as being seen in the drawings of the magnet of dc magnetic field generator 1604, is used for the installation of optical fiber 1608 and 1609.After forming magnet installation cavity and optical fiber installation groove, polarizer 1602, the unit 1601 of magneto-optic, analyzer 1603 and optical fiber 1608 and 1609 installation in substrate 190 is by installing the single optical fiber of assembling in the groove at optical fiber, using accurate diamond saw to remove to cut apart optical fiber on the surface of substrate 1690 at three grooves of direction machine work of cross-section optical fiber is four parts: optical fiber 1602,1610 and 1609, and assembling polarizer 1602 in the central portion of three grooves and magnet installation cavity respectively, the unit 1601 of magneto-optic, the magnet of analyzer 1603 and dc magnetic field generator 1604 is realized.Therefore, the magneto optical modulator of this embodiment can be produced by batch, and need not to adjust optical axis.
The magnet of dc magnetic field generator 1604 for example is a ferrite permanent-magnet iron, and it does not produce eddy current within the radio-frequency field that is produced by radio-frequency field generator 1605.
Impedance regulator 1606 is identical at those of configuration aspects and the foregoing description, and is configured in the outside of substrate 1690, but can be produced in the substrate 1690.
Dc magnetic field generator 1604 can be configured in the outside of radio-frequency field generator 1605 alternatively, therefore avoids the generation that applies caused eddy current by radio-frequency field.Therefore, dc magnetic field generator 1604 can be by realizing based on the metal of SmCo (Sm-Co) or based on the metal permanent magnet of neodymium iron boron (Nd-Fe-B).
The magneto optical modulator of present embodiment can be used for aforesaid any one light signal transmission system.
Figure 17 (a) and Figure 17 (b) illustrate the magneto optical modulator according to thirteenth embodiment of the invention.
Radio-frequency field generator 1705 is positioned on the unit 1701 of magneto-optic.Particularly, radio-frequency field generator 1705 is made up of the coil that uses irradiation and etching technique to form on the surface of the unit 1701 of magneto-optic.If realize by monomode fiber, the internal diameter of this coil preferably at 10 μ m in 100 mu m ranges, be used for the light that polymerization is come out from optical fiber 1708.If optical fiber 1708 is to be realized by multimode fiber (for example gradient index fiber) or large diameter optical fiber, the internal diameter of this coil preferably at 100 μ m between the 1000 μ m.The unit 1701 of magneto-optic is by (BiGdYLa) 3(FeGa) 5O 12Crystal film forms.The easy magnetizing axis of this garnet crystal is positioned perpendicular to its end face, is used to guarantee to respond the low level radio-frequency field and puts on this.Be similar to 1708, optical fiber 1709 can be by monomode fiber, make such as the multimode fiber or the large diameter optical fiber of gradient index fiber.
As clearly as shown in Figure 17 (b), on polarizer 1702 and analyzer 1703 the facing surfaces attached to the unit 1701 of magneto-optic.Assemble by lens 1720 through the light that optical fiber 1708 sends, make on the unit 1701 of magneto-optic, to form minimum admissible light beam.Polarizer 1702 linear polarizations are from the light of lens 1720 inputs.The light of linear polarization is by the unit 1701 of magneto-optic and the middle body of radio-frequency field generator 1705.Minimum diameter when the middle body of radio-frequency field generator 1705, the length on short limit of innermost circle that is to say coil is between 10 μ m and 100 μ m the time, its diameter of light beam that allows to pass the optical fiber 1708 made by monomode fiber and 1709 is less than minimum diameter, therefore effective modulation of setting up light.
The intensity of the field of developing at the center of radio-frequency field generator 1705 and the internal diameter of radio-frequency field generator 1705 are inversely proportional to.Therefore, be constant if flow through the current value of radio-frequency field generator 1705, the modulation degree that is produced by the unit 1701 of magneto-optic reduces with the internal diameter of radio-frequency field generator 1705 and increases.
After the unit 1701 that passes magneto-optic, as to the rotary action of its plane of polarization by analyzer 1703 on intensity to this light modulation, enter optical fiber 1709 through collector lens 1721 then.
Dc magnetic field generator 1740 is realized that by neodymium iron boron (Nd-Fe-B) permanent magnet it works to be parallel to its end face and applies the unit 1701 of Dc bias field to magneto-optic.
Impedance regulator 1706 is identical with in the above-described embodiments those in configuration aspects, work to adjust the impedance of radio-frequency field generator 1705, be used to guarantee effective transmission of high-frequency signal from the high frequency signal generator (not shown) to radio-frequency field generator 1705.High frequency signal generator is identical in configuration aspects with in the above-described embodiments those, and it is explained here in detail and omits.
The magneto optical modulator of this embodiment can modulation length be 1.31 μ m or the 1.55 μ m carrier wave until 1GHz.When the unit of magneto-optic 1701 usefulness have thickness 60 μ m (BiGdYLa) 3(FeGa) 5O 12When the garnet crystal film was made, optical loss increased above several decibels, may modulate the light of 0.7 to 0.9 μ m until the 1GHz frequency band but it becomes.
Be similar to the 12 embodiment, the magneto optical modulator of this embodiment can be produced in the single substrate, need not to use lens 1720 and 1721.In this case, because the radiation of lens 1720 and 1721, it becomes is that the internal diameter of radio-frequency field generator 1705 is necessary.When the gross thickness of the unit 1701 of polarizer 1702, magneto-optic and analyzer 1703 during less than about 0.6mm, the minimum diameter of radio-frequency field generator 1705 can be at 100 μ m within 1000 mu m ranges.
Figure 18 illustrates a magneto optical modulator according to the 14 embodiment of the present invention, and wherein unit 1801 designs of magneto-optic are as a light wave guider.
The unit 1801 of magneto-optic (that is, the light wave guider) has the length of extending along the direction of propagation of light signal, and with or single mode structure and multi-mode structure make.Usually, the length of the unit of the magneto-optic that passes through of the degree of magneto optical effect or modulation and light is proportional.Therefore, when the radio-frequency field that is produced by radio-frequency field generator 1805 was constant on level, the unit 1801 of magneto-optic was long more, and the degree of magneto optical effect is big more.Light beam met at right angles the situation of input with the input surface with the unit 1801 of the magneto-optic made from the garnet crystal film under, preferably the length of the unit 1801 of this magneto-optic was a few μ m or littler.Similarly, under the situation of YIG (Y3Fe5O12) bulky crystal, preferably the length of the unit 1801 of magneto-optic is 5 to 10mm.In addition, for example by Y 3Fe 5O 12. (YGd) 3FeO 12. perhaps (TbY) 3Fe 5O 12Be formed in and for example use the liquid phase crystal orientation to grow nonparasitically upon another plant by Gd 3Ga 5O 12The unit 1801 that forms the unit 1801 permission magneto-optics of magneto-optic on the nonmagnetic garnet substrate of making has the length of the surface extension 10 to 30mm that is parallel to substrate.
The length of unit 1801 of having passed through the angle of rotation of polarization surface of unit 1801 of magneto-optic and magneto-optic is proportional.The structure of this embodiment can produce greater than tens times common modulation degree, and the unit 1801 that allows magneto-optic is narrow with long along the length of light wave guider.Radio-frequency field is to the length direction that direction is positioned to be parallel to substantially the unit 1801 of magneto-optic that applies of the unit 1801 of magneto-optic.Therefore, cause the reduction of demagnetizing factor of the unit 1801 of magneto-optic, compare with the above embodiments, its allows to reduce the degree of radio-frequency field.Similarly, in the above-described embodiment, the unit of magneto-optic has length here, and the reduction of the demagnetizing factor of the unit of magneto-optic can be by applying the length realization that high frequency is parallel to the unit of magneto-optic substantially.
The structure of this embodiment makes the production of magneto optical modulator can produce modulation degree up to 1GHz 10%.
Be similar to the above embodiments, radio-frequency field generator 1804 is to be realized by the coil around the unit 1801 that is wrapped in magneto-optic.Polarizer 1802 and analyzer 1803 are to be placed on the end or primary flat of unit 1801 of magneto-optic.Collector lens 1820 and 1821 is configured in the outside of polarizer 1802 and analyzer 1803 respectively.Other layout is the same with in the above-described embodiments those, will omit their detailed explanation here.The magneto optical modulator of present embodiment can be used for aforesaid any one light signal transmission system.
Figure 19 (a) and 19 (b) illustrate the magneto optical modulator according to the 15 embodiment of the present invention, are wherein realized by transverse-electromagnetic (transverse electro-magnetic wave) unit as the radio-frequency field generator and the impedance regulator that use in the above-described embodiments.
The transverse electro-magnetic wave unit that is used in this embodiment shown in Figure 19 (b) extends along its longitudinal centre line, has the coaxial transverse electro-magnetic wave unit of empty cylinder through its conductor 1952 as what be illustrated by the broken lines in the drawings.
This empty cylinder has the end wall taper, is used to avoid reflection or the decay of radio-frequency field among this empty cylinder, and is retained in one of them optical modulation equipment 1910.
As being clearly shown that in Figure 19 (a), optical modulation equipment 1910 is made of the unit 1901 and the analyzer 1903 of lens 1920 and 1921, polarizer 1902, magneto-optic.
In operation, the light of incorporating into from optical fiber 1908 is converted to collimated light beam at lens 1920, and passes polariscope 1902 and make it by linear polarization.The light of linear polarization rotates as the effect of the radio-frequency field that puts on this unit 1901 experience plane of polarizations by magneto-optic, is modulated on intensity by analyzer 1921 as the effect of the rotation of plane of polarization then.The light that comes out from analyzer 1903 enters lens 1921, makes it be concentrated on the end of optical fiber 1909.At the needs that are used to eliminate to the compensation optical loss, under the situation that the unit 1901 of polarizer 1902, magneto-optic and analyzer 1903 enough approach, lens 1920 and 1921 can omit.
Transverse electro-magnetic wave unit 1946 has for example by boring two holes 1954 that cylindrical wall forms.Hole 1954 with given vertical shift is positioned in substantially the length direction perpendicular to center conductor 1952, as seeing in the drawings. Optical fiber 1908 and 1909 for example is fixed in the hole 1954 by adhesive, removes to keep within transverse electro-magnetic wave unit 1946 optical modulation equipment 1910.Alternatively, when the unit 1901 of magneto-optic was positioned within the middle body of transverse electro-magnetic wave unit 1946, the lens 1920 of optical modulation equipment 1910 and 1921 can be fixed in the hole 1954.
When high-frequency signal by when the high frequency signal generator (not shown) is imported, center conductor 1952 produces the radio-frequency field coaxial with it (promptly, the longitudinal centre line of transverse electro-magnetic wave unit 1946), high frequency signal generator is identical with in the above-described embodiment in configuration aspects.Therefore, put on magneto-optic unit 1901 radio-frequency field direction substantially with the vertical consistency (that is the direction of propagation of light signal) of optical modulation equipment 1910.When radio-frequency field puts on the direction of unit 1901 of magneto-optic when fully consistent with the direction of propagation of light signal, maximum modulation degree will be produced, yet the direction that applies when radio-frequency field is when arriving within the direction of propagation ± 15 ° scope of light signal, can not reduce modulation degree greatly.Particularly, the input direction of light beam can be located end face perpendicular to the unit 1901 of magneto-optic in ± 15 ° of scopes.
Dc magnetic field generator produces coil 1931 by dc generator 1930, D.C. magnetic field and is used to improve and applies the Dc bias field and constitute to the soft magnetic core 1932 of the efficient of the unit 1901 of magneto-optic.The Dc bias field that puts on optical modulation equipment 1910 (being the unit 1901 of magneto-optic) is to the sidewall that passes optical modulation equipment 1910 in ° scope of direction line stretcher ± 30 on any direction that applies perpendicular to radio-frequency field.
The end of transverse electro-magnetic wave unit 1946 is stopped by terminate load 1950, and terminate load is made by resistance usually, is used to avoid the reflection of high-frequency signal on the end of transverse electro-magnetic wave unit 1946.If the impedance of the impedance of the output impedance of high frequency signal generator, transverse electro-magnetic wave unit 1946 and terminate load 1950 is set to match each other, the magneto optical modulator of this embodiment can be implemented in very wide low frequency to the interior modulation of high-frequency range, and for example 0.1MHz is to 2GHz.
In this embodiment, from above-mentioned discussion, significantly find out, work the impedance regulator of the hindrance function of adjusting the radio-frequency field generator and realize by transverse electro-magnetic wave unit 1946 and terminate load 1950.
Replace terminate load 1950, transverse electro-magnetic wave 1946 these ends can short circuit, be similar to coaxial resonant cavity or have filter circuit and be provided with on it, be used to reflect signal component with distinctive frequency, therefore can make strong or high power light signal modulated on distinctive frequency.
In the structure of this embodiment, radio-frequency field produces in being shielded from electromagnetic space, makes it avoid external high frequency noise.
Typical electromagnetism metallic shield can make to spend in each of the above embodiments avoids unwanted radio-frequency field radiation.The magneto optical modulator of present embodiment can be used for aforesaid any one light signal transmission system.
Though for the ease of understanding better, disclose the present invention, should be appreciated that the present invention can be summarised in the various methods, and do not break away from principle of the present invention by preferred embodiment.Therefore, present invention is to be construed as all possible embodiment and the improvement that comprise for the embodiment that illustrates, that it can be included in the accessory claim to be stated and do not break away from principle of the present invention.

Claims (38)

1. light signal transmission system comprises:
The light source of an emission light beam;
A high frequency signal generator that produces high-frequency signal;
Modulation is from the magneto optical modulator of the light beam of described light emitted, described magneto optical modulator comprises a polarizer, the unit of a magneto-optic, an analyzer, a dc magnetic field generator, a radio-frequency field generator and an impedance regulator, the light beam of described light emitted enters described polarizer in proper order, the unit of described magneto-optic and described analyzer, this dc magnetic field generator operation is given the unit of magneto-optic to apply Dc bias magnetic field, this radio-frequency field generator response applies the unit that radio-frequency field is given magneto-optic from the high-frequency signal of described high frequency signal generator, and this impedance regulator operation is to adjust the impedance of radio-frequency field generator;
Transmission is by the optical fiber of the light beam of described magneto optical modulator modulation; With
Reception is by the optical receiver of the light beam of the modulation of described optical fiber emission.
2. one kind as the light signal transmission system that proposes in claim 1, wherein the unit of this magneto-optic is made by the multidomain magneto-optic memory technique, and wherein dc magnetic field generator produces Dc bias field greater than the saturation field of the unit of magneto-optic.
3. one kind as the light signal transmission system that proposes in claim 1, wherein the Dc bias field direction that is applied to the direction of unit of magneto-optic and the unit that radio-frequency field is applied to magneto-optic is positioned in 90 ° ± 30 ° the scope.
4. one kind as the light signal transmission system that proposes in claim 1, the direction of applying radio-frequency field wherein for the unit of described magneto-optic is the easy axis that is positioned at the unit of a described magneto-optic.
5. one kind as the light signal transmission system that in claim 1, proposes, the length direction of the unit of wherein said magneto-optic extends along the light velocity propagation direction, and wherein applying radio-frequency field, to give the direction of described magneto optical disk unit be the parallel direction of length that is positioned at described magneto optical disk unit.
6. one kind as the light signal transmission system that proposes in claim 1, wherein said optical fiber is realized by a kind of gradient index fiber.
7. one kind as the light signal transmission system that proposes in claim 1, wherein said optical fiber keeps optical fiber to realize by a kind of polarisation.
8. one kind as the light signal transmission system that proposes in claim 1, wherein this light beam is the input surface of unit that inputs to the magneto-optic of described magneto optical modulator in 90 ° ± 15 ° scope.
9. one kind as the light signal transmission system that proposes in claim 1, wherein said light source are by a realization of LED and fiber laser.
10. the light signal transmission system as proposing in claim 1 further comprises an image intensifer that is configured between described light source and the described magneto optical modulator.
11. the light signal transmission system as proposing in claim 1 further comprises lens that are configured between described light source and the described magneto optical modulator.
12. light signal transmission system as in claim 1, proposing, further comprise a coupler that is connected to described magneto optical modulator by described optical fiber, with a reflector that is configured on the end face of the unit of the magneto-optic on light beam input surface, so that produce the reflection by the light beam of the cells modulate of magneto-optic, described coupler also is connected to described optical receiver and goes to guide the reflection of the light beam of modulation to give described optical receiver.
13. one kind as the light signal transmission system that proposes in claim 1, wherein said high frequency signal generator are to be realized by the antenna that a form that is used for electric wave receives high-frequency signal, and launch this high-frequency signal and give the radio-frequency field generator.
14. the light signal transmission system as proposing in claim 13, wherein this antenna is a kind of of Yagi aerial, loop aerial and parabolic antenna.
15. the light signal transmission system as proposing in claim 1 wherein sends to described magneto optical modulator by a light beam with described light emitted in optical fiber and the lens.
16. a magneto optical modulator comprises:
A light beam inputs to its polarizer;
Reception is from the unit of the magneto-optic of the light beam of described polarizer;
Output is from the analyzer of the light beam of the unit of described magneto-optic;
Operate so that apply the dc magnetic field generator that the unit of described magneto-optic is given in the Dc bias field for one;
Operate so that apply the radio-frequency field generator that radio-frequency field is given the unit of described magneto-optic for one; With
Operation is with the impedance regulator of the impedance of adjusting described radio-frequency field generator.
17. magneto optical modulator as proposing in claim 16, wherein under the situation that does not apply the Dc bias field, the unit of described magneto-optic by have multidomain structure all magneto-optic memory technique make, and wherein said dc magnetic field generator produces the Dc bias field greater than the saturation field of described magneto-optic unit.
18. one kind as the magneto optical modulator that proposes in claim 16, wherein the Dc bias field direction that imposes on the direction of unit of described magneto-optic and the unit that radio-frequency field imposes on described magneto-optic is positioned in 90 ° ± 30 ° the scope.
19. one kind as at the magneto optical modulator that claim 16 proposes, the direction of applying radio-frequency field wherein for the unit of described magneto-optic is the easy axis that is positioned at the unit of a described magneto-optic.
20. magneto optical modulator as proposing in claim 16, the length direction of the unit of wherein said magneto-optic extends along the light velocity propagation direction, and wherein applying radio-frequency field, to give the direction of the unit of described magneto-optic be the parallel direction of length that is positioned at the unit of described magneto-optic.
21. one kind as the magneto optical modulator that proposes in claim 16, the unit of wherein said magneto-optic are by a bulk of crystal, polycrystal sintered body, crystal film and comprise the synthetic of resin and a kind of of magneto-optic memory technique of being dispersed in the resin makes.
22. the magneto optical modulator as proposing in claim 16, the unit of wherein said magneto-optic is to make with bilateral garnet crystal film.
23. the magneto optical modulator as proposing in claim 16, wherein the frequency of radio-frequency field is equal to or greater than 200MHz.
24. magneto optical modulator as proposing in claim 16, wherein said impedance regulator is to be realized by the filter that a high-frequency signal that is designed to allow pre-selected frequency therefrom passes through, and is used to described radio-frequency field generator or is designed to have the resonator of the high-frequency signal of pre-selected frequency resonance.
25. magneto optical modulator as proposing in claim 16, wherein said impedance regulator is to be designed to allow the high-frequency signal of at least two different frequencies to realize by its filter by one, and is used to described radio-frequency field generator or is designed to have the resonator of the high-frequency signal of different frequency resonance.
26. the magneto optical modulator as proposing in claim 16, wherein said dc magnetic field generator is realized by permanent magnet.
27. the magneto optical modulator as proposing in claim 26, wherein each of permanent magnet is by Ferrite Material, makes based on samarium-cobalt material with based on a kind of of NdFeB material.
28. one kind as the magneto optical modulator that proposes in claim 16, wherein said dc magnetic field generator comprise that an electromagnet and one provide the dc generator of electric current to this electromagnet.
29. the magneto optical modulator as proposing in claim 16, wherein said dc magnetic field generator forms the magnetic circuit of a closure.
30. the magneto optical modulator as proposing in claim 16, the unit of wherein said polarizer, described magneto-optic and described analyzer are made on single substrate.
31. the magneto optical modulator as proposing in claim 16, the unit of wherein said polarizer, described magneto-optic and described analyzer are to be inserted between the ruler that is provided with straight line.
32. one kind as the magneto optical modulator that proposes in claim 16, wherein said radio-frequency field generator are to be placed on the end face of unit of described magneto-optic.
33. the magneto optical modulator as proposing in claim 16, the unit of wherein said magneto-optic is positioned such that light beam inputs to an input face of the unit of described magneto-optic in 90 ° ± 15 ° scope.
34. one kind as the magneto optical modulator that proposes in claim 16, wherein said radio-frequency field generator are to be to realize to the coil within 1000 mu m ranges at 10 μ m by its minimum diameter.
35. the magneto optical modulator as proposing in claim 16, the unit of wherein said magneto-optic is to be made by a light wave guider of being made by the garnet crystal film.
36. the magneto optical modulator as proposing in claim 16, wherein said impedance regulator is made up of a transverse electro-magnetic wave unit and a terminate load.
37. one kind as the magneto optical modulator that proposes in claim 36, wherein said impedance regulator are that be designed to can be in given frequency resonance.
38. the magneto optical modulator as proposing in claim 16 further comprises an electromagnetic wave shielding shell, disposes the unit of described polarizer, described magneto-optic, described analyzer and described radio-frequency field generator therein.
CNB011393076A 2000-10-27 2001-10-26 Optical signal transmission system and wide-range magneto-optical modulator in the said system Expired - Fee Related CN1211955C (en)

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KR100425366B1 (en) 2004-03-30
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EP1640790A2 (en) 2006-03-29
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EP1202105A3 (en) 2003-12-10
DE60119259T2 (en) 2007-03-29

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